Manufacture of artificial articles from fibroin solutions



Patented Feb. 8, 1938 MANUFACTURE OF ARTIFICIAL ARTICLES FROM FIBROIN SOLUTIONS Ernst Rossner and Karl Biirner, Premnitz/Westhavelland, and Herbert Mahn and Wilhelm Irion, Dessau, Germany, assignors to I. G. Farbenindustric Aktlengesellschaft, Frankfort-ontlie-Main, Germany No Drawing. Application August 4, 1931, Serial No. 555,133. In Germany August 18, 1930 '14 Claims. Our present invention relates to the manufacture of artificial products, such as fibers, films, ribbons, tubular bodies, etc. from fibroin solutions.

One of its objects is a process for producing the said articles. Further objects will be seen from approaches that of the natural silk wound up from the cocoons with respect to strength and extensibility, fineness, feel and lustre.

A suitable precipitating bath is a concentrated solution of an inorganic salt, for instance, am-

monium sulfate, sodium sulfate, sodium and ammonium bisulfate, zinc sulfate, magnesium sulfate, an alcali metal salt of phosphoric acid. A concentrated solution of an organic salt may likewise be used, thus, for instance, a solution of 5 ammonium formate, sodium formate, sodium acetate, an alcali metal salt of oxalic acid, lactic acid, citric or tartaric acid, or a solution containing a mixture of an inorganic and an organic salt, for instance of those just mentioned.

From this great number of salt solutions we prefer the use of a concentrated solution of ammonium sulfate or of ammonium formate. An acid may be added in a suitable proportion to these baths, for instance, an inorganic acid, such as sulfuric acid, hydrochloric or phosphoric acid, or an organic acid, such as formic acid, acetic acid, oxalic acid, lactic acid, citric or tartaric acid. Preferably, however, we add sulfuric or formic acid. The amount of acid added to the concentrated salt solution may be varied within wide limits. The best kind of acid and the most suitable amount of acid to be used in combination with a particular salt solution and a particular fibroin solution may easily be determined by some comparative experiments.

By means of these baths it is possible to work up spinning solutions of the most varied viscosities, for instance, 0.5 to over 25 poises, the viscosity being determined at the temperature which is imparted to the solution before spinning.

The stretching is produced by causing the precipitating bath to act upon a long length of thread, thus stretching is gradual; also mechanical means can be used with advantage, for instance, two or several draught rollers with different peripheral velocities. In the latter case a shorter-length of immersion in the bath may be used, for'instance, 0,l1 meter, because a stretching by the coagulating liquid is necessary not at all or only to a small extent. When using several rollers with increasing peripheral velocities, the last roller is preferably given a somewhat smaller peripheral velocity than the last but one. The spun silk may be finished in the usual manner by washing, soaping and drying.

Fibroin solutions with a low content of electrolyte in the meaning as set forth may for example be prepared according to the copending application Serial-No. 531,850 filed on April 21, 1931 by Irion and Mahn or Serial No. 499,839 filed on December 3, 1930 by Fink and Ro'ssner. Solutions of fibroin in ammoniacal-cop r oxyde are also useful if the content of ammonia is reduced after complete dissolution of the fibroin in the usual ammoniacal-copperhydroxide solvent in the cold, for instance 0 C.

The following examples illustrate the invention:

(1) 1 part by weight of natural silk wastes is introduced at about 45 0. into 4- parts by'weight ofa solution of NaSCN saturated at 50 C. and the whole is allowed to stand for 30 minutes while well kneading. The paste which forms is eliminated and subjected to dialysis. In this operation a diluted fibroin solution is obtained, which is practically free from salt. The dialysed solution is concentrated to a fibroin content of about 11.5 per cent, the rest-of NaSCN still present amounts'to 0.3 per cent. This solution, having a viscosity of about 0.5-1 poise at 20 C., is spun from a. glass nozzle with 24 perforations of 0.08 mm. diameter in a precipitating bath having a length of about 3 metres and at a temperature of 20 C. and comprising an ammonium sulfate solution of about 40 per cent strength. The speed of draught amounts to 40 metres per minute in the case of a delivery which corresponds with a total titre of 50 deniers. A thread is obtained which has a dry tenacity of about 1.6 grams per denier and an extensibility of about 25 per cent. When working according. to this example, the draught can be increased to -80 metres per minute, particularly when a high total titre is being spun. (2) A fibroin solution made according to Example 1 and containing about 12 per cent of fibroin and about 0.5 per cent of NaSCN and havinga viscosity of 0.5-1 poise at 20 C., is spun from a glass nozzle with 24 perforations of a diameter of 0.08 mm. in a precipitating bath him/'- ing a length of about 3 meters and containing 50-60 per cent of ammonium formate and 3 per cent of formic acid at a temperature of 20 C. The speed of draught amounts to 20 meters per minute; the thread delivered is stretched by means of a second roller having a peripheral velocity of about 60 meters per minute; the delivery of the spinning liquid is regulated so that a total titre of 48 deniers is formed. A thread is obtained which has a dry tenacity of about 2 grams per denier and an extensibility of about per cent.

(3) A fibroin solution, prepared by dissolving fibroin in liquefied ammonia at a temperature near the freezing point of ammonia and mixing the solution of fibroin in ammonia with water while evaporating the ammonia, and containing about 16.8 per cent of fibroin and about 0.07 per cent of ammonia and having a viscosity of about 1.5 poise at C. is ejected from a glass nozzle having 120 perforations of a diameter of 0.07 mm. into a precipitating bath consisting of an aqueous solution containing about-42 per cent of ammonium sulfate and about 4 per cent of sulfuric acid. The delivery of the spinning liquid is regulated so that a total titre of 150 deniers is obtained. The length of immersion of the thread in the precipitating bath is 2.8 meters, the temperature of the bath is 20 C. After having left the bath the thread runs on a roller having a peripheral velocity of about '7 meters per minute and then on a second roller having a peripheral velocity of about 30 meters per minute. It is, therefore, stretched between the two rollers to about 4.3 times its length. There are obtained threads of a dry tenacity of about 2.5 grams per denier and an extensibility of about 18 per cent. The elasticity of the threads is the same as that of the natural silk.

(4) A solution of fibroin in ammoniacal copper-oxide, prepared at a low temperature, fromwhich, when dissolution is complete, the content of ammonia has been reduced to about 1.28 per cent, having a fibroin content of about 8.9 per cent, a copper content of about 3.0 per cent and a viscosity of 5.7 poise at 0 C., is ejected from a glass nozzle having 120 perforations of a diameter-of 0.06 mm. into an aqueous precipitating bath containing about 42 per cent of ammonium sulfate and about 4 per cent of acetic acid. The delivery of the spinning liquid is regulated so that a thread of 180 deniers is produced. The length of immersion of the thread in the precipitating bath amounts to 2.8 meters; the temperature of the bath is 20 C. The thread is drawn cif from the bath by a draught roller having a peripheral speed of about 6.0 meters per minute and then passes over a second roller or spool having a peripheral speed of about 36 meters. The thread is, therefore, stretched between two rollers to about 6 times its length. While on the spool, the thread is freed from cop per and washed by irrigation or suction with diluted acid. There are obtained threads 01' a dry tenacity of about 2.0 grams per denier and an ejected through a glass nozzle having 120 perforations of a diameter of 0.07 mm. into a precipitating bath containing about 39 per cent of ammonium sulfate and about 2.4 per cent of sulfuric acid. Ti length of immersion of the thread in the i amounts t0 2 meters, the

' The quantity of spinni andardized to a total 2 r leaving the bath, the .l runs over a draught roller having a peripnmal velocity of about meters per minute and then over a second roller having a peripheral velocity of about 22.5 meters per minute, so the ii. is stretched to about 4.5 times its length. There. are obtained threads of a dry tenac" 2.2 grams per denier and an exten about 20 per cent.

Our present invention is not limitforegoing examples or the spe given therein. Thus, for instance, othi trated salt solutions may be employed as p. itating baths. Furthermore the amount or the acid added to the salt solution may be varied to the special working conditions,

What we claim is:

1. A process. which comprises spinning a fibroin solution with a low content of electrolytes in a precipitating bath consisting of a concentrated solution of ammonium sulfate, and stretching the freshly coagulated product.

2. A process, which comprises spinning a fibroin solution with a low content of electrolytes in a precipitating bath consisting of a concentrated solution of ammonium formate, and stretching the freshly coagulated product 3. A process, which comprises spinning a fibroin solution with a low content of electrolytes in a precipitating bath consisting of a solution of ammonium formate containing at most 10 per cent of formic acid, and stretching the freshly coagulated product.

4. A process, which comprises spinning a fibroin solution containing about 12 per cent of fibroin and about 0.5 per cent of NaSCN, and having a viscosity of about 0.5 to 1 poise at 20 C. in a precipitating bath comprising 50 to 60 per cent of ammonium formate and 3 per cent of formic acid at a temperature of about 20 C., the immersion length of the formed threads inthe precipitating bath being abnut three metres, drawing off the freshly co lated threads from the spinning bath by IOllul having a peripheral velocity of about 20 meters per minute and passing the threads over a second roller having a peripheral velocity of about 60 meters per. minute.

5. A process, which comprises spinning a fibroin solution containing about 16.8 per cent of fibroin and about 0.07 per cent of ammonia, and having .a viscosity of about 1.5 poise at 20 C., in a precipitating bath comprising an ammonium sulfate solution of about 42 per cent strength and about 4 per cent of sulfuric acid at a temperature of about 20 C., the immersion length of the formed threads in the precipitating bath being about 2.8 meters, drawing off the freshly coagulated threads from the spinning bath by a roller having a peripheral velocity of about '7 meters per minute, and passing the threads over a second roller having a peripheral velocity of about 30 meters per minute.

6. A process, which comprises spinning a fibroin solution containing about 8 per cent of fibroin, about 2.7 per cent of copper and about 0.9 per cent of ammonia, and having a viscosity of about 2.5 poises at 0 C., in a precipitating bath comprising an ammonium sulfate solution of about 39 per cent strength, and about 2.4 per cent of sulfuric acid at a temperature of 18 C.,

the immersion length of the formed threads in the precipitating bath being about 2 meters, drawing off the freshly coagulatedthreads from the spinning bath by a roller having a peripheral velocity of about 5 meters per minute'and passing the threads over a second roller having a peripheral velocity of about 22.5 meters per minute. I

7. A process of producing artificial fibroin threads which comprises dissolving fibroin in an aqueous solution of an inorganic electrolyte at a temperature not higher than 80 C., removing said electrolyte from said solution so that said solution becomes substantially free from said electrolyte, spinning said solution in a precipitating bath consisting of a concentrated aqueous solution of an easily water-soluble salt and stretching the freshly coagulated product.

8. A process of producing artificial fibroin threads which comprises dissolving fibroin in an aqueous solution of an inorganic electrolyte at a temperature not higher than 80 C., removing said electrolyte from said solution so that said solution becomes substantially free from said electrolyte, spinning said solution in a precipitating bath consisting of a concentrated aqueous solution of an easily water-soluble salt and containing at most per cent of an acid and stretching the freshly coagulated product.

' 9. A process of producing artificial fibroin threads which comprises dissolving fibroin in an aqueous solution of an inorganic electrolyte at a temperature not higher than 80 C., removing said electrolyte from said solution so that said solution becomes substantially free from said electrolyte, spinning said solution in a precipitating bath consisting of a concentrated aqueous solution of an easily water-soluble inorganic salt and stretching the freshly coagulated product.

10. A process of producing artificial fibroin threads which comprises dissolving fibroin in an aqueous solution of an inorganic electrolyte at a temperature not higher than 80 C., removing said electrolyte from said solution so that said solution becomes substantially free from said electrolyte, spinning said solution in a precipitating bath consisting of a concentrated aqueous solution of an easily water-soluble inorganic salt and containing at most 10 per cent of an acid and'stretching the freshly coagulated product.

11. A process of producing artificial fibroin threads which comprises dissolving fibroin in an aqueous solution of an inorganic electrolyte at a temperature not higher than 80 C., removing said electrolyte from said solution so that said solution becomes substantially free from said electrolyte, spinning said solution in a precipitating bath consisting of a concentrated aqueous solution of ammonium sulfate containing at most 10 per cent of sulfuric'acid "and stretching the freshly coagulated product.

12. A process of producing artificial fibroin point of ammonia, mixing the solution of fibroin and ammonia with water while evaporating the ammonia, spinning said solution in a precipitating bath consisting of a concentrated aqueous solution of an easily water-soluble salt and v stretching the freshly coagulated product.

14. A .process of producing artificial fibroin threads which comprises dissolving fibroin in an aqueous ammoniacal copper-oxide solution at a temperature below 0 C., evaporating the superfluous ammonia, spinning the solution in a. precipitating bath consisting of a concentrated aqueous solution of an easily water-soluble salt and stretching the. freshly coagulated product.

ERN-ST RossNEa 

